Jet propulsion engine for model airplanes



April 3, 1951 J. B. ROBINS JET PROPULSION ENGINE FOR MODEL AIRPLANES Filed Dec. 12, 1947 INVENTOR. JA or 5. Ros/Ms.

ATTO

Patented Apr. 3, 1951 UNHTED s'rA'rss ATENT OFFICE JET PROPULSION ENGINE FOR MODE AIRPLANE S 3 Claims.

, plane engines and has reference more particularly to a conversion unit for model airplanes.

There are on the market today small gasoline engines for use with model airplanes and there is also a large number of persons whose hobby is constructing toy airplanes.

Model airplanes are, as a rule, powered by small gasoline engines employing propellers that provide the propulsive force.

Jet engines have been used with full size airplanes and model airplane fans are interested in this method of propulsion. I

It is the object of this invention to produce a jet engine employing as one element an ordinary miniature gasoline engine to which is applied a conversion element that converts it into a jet type engine.

In order to describe the invention so that its construction and mode of operation can be readily understood, reference will be had to the ac companying drawing in which the invention has been illustrated and in which:

Figure 1 is a longitudinal diametrical section taken on line Figure 2;

Figure 2 is an end view looking through plane 2 in Figure l; I

Figure 3 is a view, partly in elevation and partly in section, taken on line 33, Figure 4, showing an automatic spark advance device; and

(Cl. (iii-35.6)

which contains the engine and the other, which has been designated by reference numeral ll, serves as a fuel reservoir. A pipe l8 extends from the lowermost point of the fuel reservoir and projects through the tapered end of the housing, terminating at I9. A combined fill and vent pipe 253 communicates with the fuel reservoir. The engine illustrated-is of the two-cycle type and has its exhaust port in communication with the outside of the housing by means of a tube 2|. The spark plug has been designated by reference numeral 22. The timer has been shown in a general way in Figure l and has been indicated by reference numeral-23. The construction of the timer has been shown in detail in Figures 3 and 4 to which reference will herein- Figure 4 is a longitudinal diametrical section taken on line 44, Figure 3.

Referring now to the drawing, reference numeral l0 designates an internal combustion enthis instance, is one of the miniature engines manufactured and sold for use in connection with model airplanes. Such engines employ gasoline as fuel and are each provided with a carburetor H. The crank shaft carries at its forward end a propeller :2. The engine is positioned within a housing that has a shape substantially like that shown in Figure 1 and which will be referred to as pear shaped. The front end i3 is open and the rear end, which has been designated by reference numeral M, is pointed. The engine is secured in the housing by means of suitable brackets like those designated by reference numeral [5. The housing is made in two parts, the rear part being designated by A and the front part by B. The cylinder projects through an opening in the engine housing as shown in the drawing. A partition It extends across the interior of the engine housing and divides the latter into two compartments, one of after be made.

A. combustion chamber comprising an elongated cylindrical tube 24 is connected at its front end to the rear end of the engine housing as shown at 25.

The engine housing is enclosed in an outer housing of substantially the same general outline, but of larger dimensions. This housing has been designated by reference numeral 26 and is secured to the engine housing and held in predetermined spaced relation therewith by means of a plurality of struts 21. Housing 26, like the engine housing, is made in two parts, the parts being designated by reference characters C and D. The two parts are interconnected as indicated at 28. The front end of section D of housing 26 is reversely curved as shown at 29. There is a gap between the front end of the engine housing and the reentrant portion of the housing in a manner clearly shown in Figure 1. The propeller is positioned in line with the space between the two housings and has a plurality of blades 30 that have their outer edges curved forwardly as indicated at 3|. This propeller acts both as an impeller and as a propeller. The impeller action forces air outwardly into the space between the two housings and the impeller action drives air rearwardly into the engine housing building up a supply of air under somewhat increased pressure from which the engine receives its air supply, the increased pressure serving, in a degree, to effect a supercharge.

Housing 26 tapers rearwardly and terminates in a cylindrical portion 32 that fits the outer surface of the combustion chamber and may be welded or otherwise permanently attached to the latter. Spacer plates 33 are provided between the inner surface of housing 26 and the outer surface of the combustion chamber soas to hold asezoee 3 the parts in a predetermined relative position. That part of the combustionchamber wall between points 32 and 25 is foraminated so that the air that is delivered into the space between the two housings may enter the combustion chamber near its front end. A stream of air blowing rear wardly around the tapered end of the engine housing or the fuel reservoir will produce a suc tion that transfers liquid fuel from the reservoir and discharges it into the stream of air that enters the front of the combustion chamber. The spark plug 36 is positioned in the wall of the combustion chamber and serves to ignite the gaseous mixture that flows rearwardly. When this mixture is ignited, its volume will expand due to'the heat and the resultant gases will emerge in the form of a jet through the rear end of the combustion chamber. The jet produces a reaction that tends tomove the assembly forwardly or to the right when viewed as in Figure 1. After the gases have been ignited they will, of course, continue to burn without the necessity of igniting them continually and therefore any erence numeral 36 which are applied thereto after a l has been inserted in 25.

The assembly shown in Figures 1 and 2 and which has been described constitutes the power plant for model airplanes and when of suificient size may also be employed on full-sized planes. The ignition of the engine is controlled by means of a circuit making and breaking device that is so constructed that it will automatically advance the spark as the speed of the increases. This timing device has been illustrated in Figures 3 and 4 to which reference will now be made.

Referring now to Figure 4, reference numeral 3i designates a part of the crank case through which the crank shaft 38 extends. A bushing 35} lines the opening in tubular extension 3'1 and forms a bearing for the crank shaft as shown in Figure e. One part of the circuit maker ant breaker is mounted for rotation on the bushing. This part consists of a ring-like portion 68 having a propeller blade 4i extending radially therefrom. A spring 42 has one end attached to member 3i at 43 and the other end attached to 46. Spring 12 is so wound and tcnsioned that it tends to rotate the propeller blade in a counter clockwise direction when viewed as in Figure The engine is provided with a stop has been designated by reference numeral 43a that limits secured to the crank shaft and held aga rotation thereon by means of a spline e5. ii) provided with an upwardly eXten' bracket 4%. This bracket has an arm that tel 'nates in a forwardly projecting portion t! that part of the cam passes the hook 53. As soon as the high portion of the cam comes into position, it will open the circuit. The opening and closing of the contacts controls the operation of the spark plug. Since shaft 38 rotates in a countercloclw s ection when viewed as in Figure 3, the spark will advance when blade 4| moves in a clockwise direction in response to the air currents produced by the fan and therefore the will be advanced as the speed of the engine increases. The engine is started in the manner now employed in connection with engines of this type and after it has been put into operation, the parts will function first to suck air in through the front end of the assembly making the same through the space between the two housings and into the combustion chamber where it will mix with the fuel sprayed thereinto through the end of pipe is. The ignition of the fuel will produce the jet and the reaction to which reference has already been made.

Units like that described above can be sold independently of the engine and the latter positioned therein, thereby making it possible to convert the ordinary small typed. gas line engine into a type engine, thus obtaining increased eniciency and propelling force.

Having described the invention what is claimed as new is:

1.. A jet type engine for airplanes comprising, an engine having a crank shaft, a pear-shaped housing enclosing the engine, means for supporting the engine in the housing with the crank shaft substantially coincident w'iththe axis of the housing, the huge end of the housing being open, the engine havin a carburetor positioned in the housing, a propeller on the crank shaft in front of the open end of the housing in position to receive air, the engine having an exhaust port in communication with the outside of the housing, the rear end of the housing having a transverse partition forming a fuel reservoir, a second housing having its front end enclosing the engine housing in spaced relation, the forward end of the second housing being open and terminating adjacent the front of the propeller, whereby air directed radially from the propeller will enter the space between the housings, an elongated rearwardly extending tube having a reaction nozzle at its rear end and forming a combustion chamber forwardly thereof, the forward end of the tube having a foraminated wall, a portion of which is disposed about the rear end of the first named housing, the second named housing having a portion spaced outwardly from the foramihated. wall and terminating adjacent the rear end thereof, and conduit means communicating the fuel reservoir with the combustion chamber,

2. A jet engine for airplanes comprising, a substantially pear-shaped engine housing having its enlarged end open, an internal combustion engine positioned in the housing with its crank shaft coaxial therewith, the tapered end of the housing having a transverse partition forming with the wall of the housing a fuel compartment, a tube communicating the lowermost point of the fuel compartment with the outside of the point of the taper, a tubular combustion chamber having its front end attached to the engine housing, its rear end forming a reaction nozzle, the end of the fuel tube communicating with the interior of the combustion chamber at the front end of the latter, an outer rearwardly tapering housing, enclosin the engine housing, means for holding the two housings in predetermined spaced relation, comprising a plurality of rigid struts, the rear end of the outer housing being connected with the combustion chamber at a point to the rear of its front end, the portion of the combustion chamber Within the outer housing being foraminated, and a propeller on the front end of the crank shaft for directing air rearwardly into the engine housing and into the space between the housings.

3. A unit for converting an internal combustion type reciprocating engine into a reaction engine of the jet type, comprising, a substantially pearshaped engine housing open at its larger end, a partition extending across the interior of the housing dividing it into an engine compartment and a fuel compartment, an elongated tubular member having its front end attached to the rear end of the engine housing forming a combustion chamber and its rear end forming a reaction nozz le, a housing of approximately the same shape as the engine housin enclosing the latter in spaced relation, means comprising a plurality of struts interconnecting the two housings to hold them in REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date Number Name 1,092,255 Gering Apr. 7, 1914 1,343,943 Thompson June 22, 1920 2,024,274 Campini Dec. 17, 1935 2,383,385 Heintze Aug. 21, 1945 2,421,518 Molloy June 3, 1947 

